WASHINGTON — The White House's top scientist says the debate about climate change is no longer a conversation about America's future, but about how the country will react to dramatic changes to the environment that are already happening.

On Tuesday, the Obama administration released its third National Climate Assessment, a cross-agency government report detailing climate change and its effects on the American populace. President Obama's science adviser, John Holdren, said that the report found real impacts on Americans from climate change, from disruptions to the water supply to more severe allergy attacks.

"The contents confirm climate change is not a distant threat. It is affecting the American people already," Holdren said in a White House video about the assessment shared first with BuzzFeed.

"On the whole, summers are longer and hotter, with longer periods of extended heat. Wildfires start earlier in the spring and continue later into the fall. Rain comes down in heavier downpours," Holdren said. "People are experiencing changes in the length and severity of seasonal allergies. And climate disruptions to water and agriculture have been increasing."

Behind the changes to the climate is human activity, Holdren said.

"These phenomena are consistent with the ongoing changes in global climate, which we know with very high confidence are being caused mainly by the increase of atmospheric carbon dioxide and other heat-trapping gasses released by human activities," he said.

The video is part of an extended push by the White House this week to put climate change on the American agenda despite reticence from Republicans on Capitol Hill. In addition to the report — which launched on a slick government website called GlobalChange.gov — top Obama adviser John Podesta is hosting an event at the White House focusing on how climate change is impacting specific regions of the United States.

On Thursday, the Weather Channel will host a Google Hangout at the White House featuring top administration officials discussing climate change. Obama will sit for interviews with local meteorologists from around the country Tuesday afternoon in the Rose Garden.

The administration promises real action on climate change despite the essential impossibility of climate legislation moving through the divided Congress.

Evan McMorris-Santoro is the White House correspondent for BuzzFeed News.